For the purposes of clarity only, the present invention will be described in the embodiment of a method and apparatus for applying nitrogen, nitrate inhibitor or weed spray to an area of interest in the form of a pasture. However as will be appreciated by those skilled in the art, the present invention may be suitable for the selective application of different substances to any area of interest.
The application of nitrogen and nitrate inhibitor to a pasture is known in the art of pastoral farming. Current practice is for nitrogen to be distributed evenly across a field or pasture to promote growth of the desired crop species. Typically, a number of samples are taken to determine the level of nitrogen to be applied. The disadvantage of this approach is that this very broad-brush method of sampling does not take into account relatively small randomly located spots that may have a high localised level of nitrogen Such small spots of high nitrogen arise due to, for example, animal excrement or decomposition of organic matter. Under the current approach, these spots have yet further nitrogen added. This is both an additional cost to the farmer and can be a source of nitrates leaching into nearby waterways and aquifers.
Equally, the application of nitrate inhibitor to a pasture is currently performed by evenly distributing nitrate inhibitor across the field or pasture, without account for localised areas of high nitrogen.
Methods of detecting areas of high nitrogen are known in the art, however most are complex and involve the testing of soil and plant tissue. One method which does not use chemicals, relies on the effect of nitrogen on the growth rates of plants. Plants growing in areas having a high level of nitrogen will grow much more rapidly than plants growing in areas having a low level of nitrogen in the soil. Therefore, by analysing the relative growth of plants across a field or pasture, the regions having high levels of nitrogen can be determined. The only method known to the applicant for selectively applying nitrate inhibitor to these areas of high nitrogen is to manually apply nitrate inhibitor to those areas exhibiting more rapid plant growth.
Methods for differentiating plants from their surroundings are known in the art, one such example is detailed in NZ 254659. This patent specification discloses an apparatus which projects two wavelengths of light which are readily absorbed by the chlorophyll in plants and wavelengths of light which are strongly reflected by the chlorophyll in plants. By analysing the light reflected, the apparatus is able to determine both the presence and size of a plant due to the amount of light absorbed by the chlorophyll. The apparatus of NZ 254659 describes a method for the application of weed spray to plants which meets a certain user calibrated threshold of reflected chlorophyll absorbent light to reflected non chlorophyll absorbent light (i.e. the condition that exists when a plant is detected). The disadvantage of systems such as NZ 254659 are that they are only capable of selectively applying a substance such as a weed spray to areas when certain conditions are determined to exist. However, it would be useful if in some circumstances an apparatus could instead be easily reconfigured to continually apply a substance unless certain conditions are determined to exist or not exist.
All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.
Throughout this specification, the word “comprise”, or variations thereof such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.